mon: use `_current_monitor_address` in systemd unit file
mon: use `_current_monitor_address` in systemd unit file

Let's avoid a jinja loop and use `_current_monitor_address` to get the
monitor address.

Signed-off-by: Guillaume Abrioux <30a9df5a0293a6108675377fa1673f7aa713f915@redhat.com>

fgal/ceph-ansible,ceph/ceph-ansible,ceph/ceph-ansible,fgal/ceph-ansible